The invention relates to machinery for the reduction of tires to small pieces and in particular to a tire shredding machine with rotary cutter assemblies which are stronger, more easily sharpened, and which can be assembled, repaired and replaced in-situ on a drive shaft.
In U.S. Pat. No. 3,931,935, M. Holman teaches a method of cutting tires using cutting wheels which intermesh with other wheels of similar dimensions, using shearing action between the intermeshing wheels as the cutting force. Holman realized that because of the toughness of tires, the outer surface of the cutting wheels would be worn. In FIG. 5 of his patent, Holman shows a cutter wheel with a sawtooth shaped outer peripheral surface. To this outer peripheral surface, strips of chrome alloy tool steel are attached. The length of each strip is greater than the length of the chordal segment on the outer peripheral surface of the disk, creating a shingling effect. An advantage of using the strips is that they can be removed, repaired and replaced after becoming worn.
The shearing wheels shown in the Holman patent are mounted on shafts with multiple wheels spaced apart from each other at precise intervals. A first set of wheels on a first shaft is spaced apart from a second set of wheels on a second shaft. The two shafts have interleaving wheels, with the interleaving distance set by spacers. The two shafts are spaced from each other a distance so that edges of the wheels pass each other, coming very close at each side, so that a shearing relation exists between the first and second sets of wheels. The xe2x80x9ccuttingxe2x80x9d of tires into reduced size pieces is achieved by shearing done by wheel edges, mainly near the radial outer periphery of the wheel, involving the outer peripheral side and top wall surfaces where most of the wear of this equipment would occur.
FIGS. 6 and 7 of the Holman patent show disks with spiked gear edges are mounted on shafts and laterally spaced apart a distance which allows the disks to act as stripper rolls in spaces below the interleaving wheels so that there is a double interleaf. First, opposed cutter wheels interleave with each other. Secondly, opposed cutter wheels interleave with stripper rolls. The function of the stripper rolls is to remove strips of sheared tires, usually about 6 to 42 inches in length and 6 inches in width. Since it is desirable to achieve a greater size reduction than this dimension a secondary set of cutter wheels, i.e. a secondary shear, follows the primary set, i.e. a primary shear, with both sets having a similar cutting action. The secondary shear reduces the 6 to 42 inch pieces to smaller pieces. In some situations even further reduction is achieved with a tertiary shear.
FIGS. 1 and 2 herein show a typical tire reduction system as used today. A continuous feed of tires, 15, is placed on conveyor belt 10 for motion toward the primary shear 11. A toothed feeder wheel 13 seizes tires from the conveyor belt and pushes them into the primary shear 11. Stripper wheels are not shown. The primary shear, relying on cutter wheels 17 and 19, reduces full tires to 6-42 inch strips 21, which are typically 6 inches wide, and a second conveyor belt 20 moves the tires to secondary shear 23. Here, a pair of rotary cutter wheels 26 and 28, mounted within box 27, held by support rails 29, receives the various length strips from bin 25. The secondary shear 23 reduces the pieces to 2-4 inch pieces 32 falling onto conveyor belt 30. Electric motors 31 provide the force for driving the primary and secondary shears simultaneously in tandem.
In FIG. 3, detailed operation of a rotary shear is seen. A first cutter assembly 17 is shown meshing with a second cutter assembly 19. Each cutter assembly is mounted on a drive shaft and has shearing knives 33 mounted adjacent to an annular spacer 35, separating the cutter assembly from an adjacent cutter assembly. The annular spacer is driven by a drive shaft by key members 37. Bolts joining the annular member to the cutter assembly allow the shearing knives to be individually removed from the cutter assembly 35 for resharpening, following the teachings of U.S. Pat. No. 4,901,929 to R. Barclay. First and second sets of cutter knife assemblies mounted on respective shafts in interleaving relationship act as rotary shears for tires fed between is the assemblies in the direction of arrow A. The stripper rolls 41 and 43 clear the spaces between spaced apart shearing knives of each shearing wheel 17 and 19. Arcuate steel segments 45 and 47 in each roll are side mounted to an annular member 49 for ease of maintenance as described in U.S. Pat. No. 4,776,249 to R. Barclay.
It is known in the prior art that the widths of the cutter wheel spacers may be graduated in thickness so that when a wheel is ground on a side, its spacer may be substituted for a neighboring thicker spacer. That wheel is also ground down on a side and is substituted for a neighboring thicker spacer, and so on. U.S. Pat. No. 4,560,112 to Rouse teaches a method of sharpening cutter wheels by removing worn cutter segments, grinding lateral surfaces and then fastening the cutter segments on a next thinner one of the cutter spacers.
A problem which still exists is the maintenance of the knives and the mounting and maintenance of spacers. An object of the invention was to simplify knife maintenance when spacer maintenance was not necessary.
Another problem which exists is that multiple cutter assemblies on a drive shaft can typically weigh 15 tons. To repair such a large piece of equipment in the field is difficult because if the cutter assemblies are removed from their support structure for repair there is frequently no suitable support for field repair and the equipment must be trucked to another location. An object of the invention was to devise cutter assemblies which could be repaired in-situ, i.e. with rotary shafts in place within their support structure.
The above object has been achieved with a new knife and spacer construction for shearing wheels of a tire shredding machine wherein repair of cutter assemblies can be done in-situ. The new knife construction involves segmented knives, with each knife segment occupying a sector of a circle as in the prior art, but with each knife having a separately demountable knife base and a removable, radially outward knife top over the knife base. Having both a demountable knife base and a removable knife top allows for selective maintenance on tire cutter assemblies. The knife base is connected at its radially inward portion to adjacent spacers and to other knives by an alignment rod parallel to an axis of rotation of the knife assembly, driven by keys in the spacers that engage keyways in the shaft, while the knife top is connected to the knife base by radial fasteners. Thus, the knife tops, which experience more wear because they are in radially offset relation to each other and have upper surfaces and part of a forward surface exposed, forming a tooth, may be sharpened without removing knife bases. However, the knife bases may also be resurfaced by removing the alignment rods without moving the main drive shaft.
It is important to note that the knife assemblies are not tied to the drive shaft but to the spacer groups. The spacer construction involves different types of segmented spacers, some of which are split in halves in their direction of rotation. The split halves are offset from each other by a half length. This allows the two halves to be welded together with exceptionally strong welds, without concern for radial shrinking after cooling because of a relieved contact surface. Radial shrinking would cause a completed cutter assembly to grip the shaft tightly and when alignment rods were loosened later, clearance needed for maintenance would be absent. By providing some spacers with this welded split construction, knife assemblies and spacers are held to the drive shaft more positively, and drive the knife assemblies which are tied to the spacers.
The rotary shaft, which drives the cutter assemblies, has 6 parallel axial keyways about the shaft, which seat three types of spacers. A first spacer is a fixed registering spacer disposed in the center of the shaft and imbedded into the shaft. A second spacer is a linearly rounded segmented spacer, with each segment having a key fitting into an axial keyway of the shaft, able to pop off of the drive shaft but for alignment rods which hold the segments in place. A third type of spacer is a welded spacer with offset segments described above. This novel spacer construction is remarkably strong and is welded after the assembly of other segments and knife components. All segments have aligned holes which allow the alignment rods to pass through, from one end of the drive shaft to the other, parallel to the drive shaft. The alignment rods secure knife bases to the spacers, with the spacers being driven by the rotary main shafts by keys fitting into keyways on these shafts. The spacers should not have to be routinely removed. However, if such action becomes necessary, for example to replace badly broken knife bases which cannot be removed in-situ, all spacers, as well as the central registering spacer, may be removed from the drive shaft, without removing the drive shaft from its support structure, thereby allowing in-situ replacement of knife bases or spacers.
The entire tire shredding assembly consisting of cutter knives and spacers, all mounted over a drive shaft become more modular with the present invention. Assembly of the apparatus is easier. Note that there are no carrier wheels for the knife components. Spacers act as drivers for knife bases and knife bases act as carriers for knife tops.